Complete the ICE chart and calculate the equilibrium constant for the formation
ID: 1084220 • Letter: C
Question
Complete the ICE chart and calculate the equilibrium constant for the formation of FeSCN2+ c. Complete the table below. It contains information that you will use in Part 1 of the experi- ment. Since [Fe]>> [SCN-], you should assume that all of the KSCN forms FeSCNa Show your work below the table beside the letter corresponding to each blank cell. 3. Table I:Standard Solutions Tube | 0.20 M Fe(NO), | 0.00050 M KSCN | 0.10 M HN03 | moles (SCN-) | [SCN-, | [FeSCN2+]eq fl(ml) mol) 0.0 1.0 (mL) 5.0 4.0 blank 5.0 | 5.0 × 10-1 | 5.0 × 10-s | 5.0 × 10-5 5.0 5.0 l.0 a) d) g) b) c)Explanation / Answer
3. Data table
moles [SCN-] = moles [FeSCN2+] = Molarity of KSCN x volume of KSCN
molarity [SCN-] = molarity [FeSCN2+] = moles [SCN-]/total volume of solution
a) 0.0005 M x 0.002 L = 1 x 10^-6 mol
b) 0.0005 M x 0.003 L = 1.5 x 10^-6 mol
c) 0.0005 M x 0.004 L = 2 x 10^-6 mol
d) 1 x 10^-6 mol/0.010 L = 1 x 10^-4 M
e) 1.5 x 10^-6 mol/0.010 L = 1.5 x 10^-4 M
f) 2 x 10^-6 mol/0.010 L = 2 x 10^-4 M
g) 1 x 10^-6 mol/0.010 L = 1 x 10^-4 M
h) 1.5 x 10^-6 mol/0.010 L = 1.5 x 10^-4 M
i) 2 x 10^-6 mol/0.010 L = 2 x 10^-4 M
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2. here again SCN- is the limiting reagent
Absorbance = 2 - log(%T) = 2 - log(12.3) = 0.9
from literature molar extinction coefficient for [FeSCN2+] = 7000 M-1.cm-1
equilibrium concentration [FeSCN2+] = absorbance/molar extinction coefficient
= 0.9/7000 = 1.3 x 10^-4 M
ICE chart
Fe3+ + SCN- <====> [FeSCN2+]
Initial (M) 0.002 M x 5 ml/10 ml 0.002 M x 3 ml/10 ml -
= 1 x 10^-3 = 6 x 10^-4
Change (M) -1.3 x 10^-4 -1.3 x 10^-4 +1.3 x 10^-4
Equilibrium (M) 8.7 x 10^-4 4.7 x 10^-4 1.3 x 10^-4
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c. equilibrium constant Kc
Kc = [FeSCN2+]eq/[Fe3+]eq.[SCN-]eq
= 1.3 x 10^-4/(8.7 x 10^-4)(4.7 x 10^-4)
= 318
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